Lactura nalli Matson & Wagner

Matson, Tanner A., Wagner, David L. & Miller, Scott E., 2019, A Revision of North American Lactura (Lepidoptera, Zygaenoidea, Lacturidae), ZooKeys 846, pp. 75-116 : 75

Lactura nalli Matson & Wagner sp. n. Figs 2, 9-14, 21, 23, 34, 38, 48, 51, 52, 60, 63, Table 1

Diagnosis.

Adult Lactura nalli are similar to L. basistriga , and in some cases indistinguishable. The following generalizations can be made when comparing series of adults: when the red basal streak is present, it is almost always shorter, usually ending before the most basal antemedial spot; the antemedial wing spots tend to be more reduced; and the hindwings are more roseate and given to pink, while those of L. basistriga are more orange-red in hue. L. nalli can be distinguished from L. rubritegula by the absence of red tegular scales (that are visible in dorsal view). Like L. basistriga , many individuals can be differentiated from L. rubritegula by a reduced upper postmedial spot and the convex arc facing the termen of the three lower postmedial spots. L. nalli can be separated from L. subfervens by the absence of the scattered flecking of red or brown scales over the forewing. Female genitalia overlap with L. basistriga but differ from other Lactura in having 4-5 anterior whirls present in the spiraled ductus bursae. Larvae can be immediately distinguished from those of other North American Lactura by their green semitransparent dorsum lacking any black or white markings, which is in stark contrast to the dark dorsum of L. basistriga .

Description adult.

(Figs 2, 21) Forewing length: male: 8.5-9.5 mm (n = 21); female: 9-10 mm (n = 8). Body salmon red. Head. Shiny, white decumbent scales over vertex and frons. Labial palpi fuscous red, straight or slightly porrect. Antenna filiform, 0.6 length of forewing; shiny, white decumbent scales over scape and basal 1/3, transitioning to fuscous to orange scales; fuscous beneath. Thorax. Patagium mostly white; red basally, most apparent around perimeter of eye. Tegula white with small ventral red basal patch. Subtriangular medial mesothoracic red spot flanked posterolaterally by ellipsoid to bar-like red spots. Coxa and femur with reddish mesal surfaces, distal and ventral surfaces with admixture of white and red scaling; tibia given more to white scaling; protarsus mostly red, meso- and metatarsus given to more white scaling. Forewing. Pearly white, with seven blood- to mahogany-red spots in oblique antemedial and postmedial series; without scattered dark scales (of L. subfervens ); antemedial row with three spots, postmedial row with four spots. Lower three spots of postmedial row forming straight line or more commonly a convex arc (closed to termen); on average, spots more reduced than those of L. basistriga (when comparing series). (These same three spots often form concave arc, open to termen, in L. rubritegula due to a more distal displacement of the lowermost spot.) Basal, subcostal red dash, typically ending before basal antemedial spot; this dash always present in males but usually absent in females. Basal red scaling along costa often narrows and ends before antemedial spots. Underside light red with pale fringe scales. Hindwing. Pinkish red in fresh individuals; dull red below but paler along inner margin. Abdomen. Dorsum and sides dull orange-red; venter rusty white. Two pairs of subventral intersegmental hairpencils (with 40-60 androconial scales) inserted between A6 and A7, and A7 and A8 (Fig. 34). Male Genitalia (Fig. 23) (n = 1). As in L. basistriga . Female Genitalia (Fig. 38) (n = 1). As in L. basistriga .

Description of living final instar.

(Figs 48, 51) Ground color glossy green with green semitransparent dorsum, lacking pale addorsal stripes and black dorsal pigmentation of L. basistriga , and brick-red to black dorsal coloration of L. rubritegula . Alimentary canal visible as a pseudo-middorsal stripe (viewed through transparent heart). Thick white subdorsal stripe punctuated by raised yellow warts with D2 setae borne from apex. Subdorsal warts on A9 yellow, never orange-yellow as in L. basistriga or black as in L. rubritegula . Two, wavy-edged, pale, supraspiracular stripes extending from T1-A8. Prothoracic shield well differentiated, medially divided, partially melanized, with little pigment deposition along its anterior and lateral margins. Head brown, partially retracted into prothorax.

Type material.

Holotype male, dry pinned, TX: Starr Co., Falcon Heights (26.5585N, 99.1220W), 05 March 2018, Berry Nall coll., Deposited at USNM, Washington D.C., USA. Paratypes adults (18♂, 8♀): TX: Starr Co., Falcon Heights (26.5585N, 99.1220W), 25 February 2018 - 19 March 2018, Berry Nall coll., BBN18#01, BBN18#05, BBN18#06 (6♂, 5♀) (UCMS); TX: Starr Co., Falcon Heights (26.5337N, 99.1059W), Berry Nall coll., BBN14#06c, (ex-ova; 30 March 2014) emerged 11 June 2014, reared on Sideroxylon celastrinum , genitalia slide # TAM–2017– 014, CO1 Barcode DLW– 000486 (1♂) (UCMS); TX: Starr Co., Falcon Heights (26.5337N, 99.1059W), Berry Nall coll., BBN14#06a, (ex-ova; 30 March 2014) emerged 27 May 2014, reared on Sideroxylon celastrinum , Voucher Code TAM0011 (1♀) (UCMS); TX: Starr Co., Falcon Heights (26.5337N, 99.1059W), 19 March 2014, Berry Nall coll., genitalia slide # TAM–2017– 013, CO1 Barcode DLW– 000569 (1♀) (UCMS); TX: Starr Co., Falcon Lk. (26.559N, 99.125W), 19 March 2018, Jim Vargo coll. (11♂,1♀) (USNM) (TAMUIC).

Other material examined.

Adults. TX: Starr Co., Falcon Heights (26.5585N, 99.1220W), 27 February 2018, Berry Nall coll. (1♂); TX: Starr Co., Falcon Heights (26.5585N, 99.1220W), 06 March 2018, Berry Nall coll., BBN18#07 (1♂) Larvae. TX: Starr Co., Falcon Heights (26.5337N, 99.1059W), ex-ova from female 25 February 2018 - 6 March 2018, BBN18#01, BBN18#05, BBN18#06, BBN18#07, Berry Nall coll., (n~60) (UCMS).

Etymology.

We name this new species after our colleague Berry Nall who provided the majority of type material, reared four clutches of larvae, and first photographed the larva.

Distribution and biology.

So far as known, L. nalli and L. basistriga are allopatric in south Texas, with L. basistriga being limited to Tamualipan communities of the lower eastern Rio Grande Valley, and L. nalli restricted to the Chihuahuan scrub areas of the western end of the Valley (Fig. 52). The east and west ends of the Rio Grande Valley differ substantially in habitat: the east end is subtropical with palm forests and dry to mesic scrub thickets, while the west end (e.g., Starr County) is drier and more typical of Chihuahuan desert communities. Many species of plants and animals occur at one end of the Valley and not the other. While our collections are limited for L. nalli , peak activity of L. nalli appears to be from February through March when spring rains are frequent and Sideroxylon celastrinum is flushing new leaves (Fig. 60).